In recent years there has been an ever increasing choice for consumers who wish to quench their thirst with ready made beverages. Many of those are now turning from the well known soft drinks to tea based beverages, be those carbonated or still, and the "natural" refreshment they can provide.
Tea contains a complex combination of enzymes, biochemical intermediates and structural elements normally associated with plant growth and photosynthesis. There are also many natural substances that give tea its unique taste, astringency, aroma and colour. Many of these are produced by the oxidation reactions that occur during the so-called fermentation stage of black tea manufacture. Tea production has long been driven by traditional processing methods with only a fundamental understanding of the chemistry that is involved. As a consequence manufacturers have discovered making ambient stable tea based beverages at the volumes required to compete with more traditional soft drinks is not simply a matter of flavouring a soft drink with tea.
The flavour of a tea based beverage and its stability rely on the stability of the beverage as a whole. It is therefore critical to preserve the quality of the beverage. The yeasts and moulds that can grow in tea based beverages and other soft drinks can be killed or controlled by heat treatment or by use of preservatives. Some tea based beverages are therefore pasteurised and then bottled in glass or special heat stable PET containers. This is known as "hot filling". Unfortunately this can be an expensive operation which creates a great deal of environmentally unfriendly waste. It has therefore become more attractive for manufacturers to pack their tea based products in standard PET containers which can range from single serve units to multi-serve packs and maintain the stability of the product using tailor made flavour and preservative systems. This is known as "cold filling". It is also useful in that one can readily use a tea concentrate or powder.
Unfortunately the use of common preservatives can affect the flavour of a tea based beverage. This is particularly true for sulphite and sorbate. Adding a strong flavour such as lemon can offset the preservative taste. However consumers are keen to experience other flavours. Furthermore, some of those consumers that were drawn to tea based products as a more healthy and natural alternative to soft drinks sometimes view preservatives as the sort of synthetic additives they would rather avoid.
Many countries have regulations that prohibit the use of certain food additives, including some preservatives, in foods and beverages. Regulations can vary widely but there is a clear trend for foods to contain fewer and lower levels of chemical preservatives, particularly synthetic ones.
Accordingly there is a need for pleasantly flavoured, ambient-stable, tea based beverages that have low levels of synthetic preservatives.
One strategy for avoiding the use of synthetic chemical additives is to use naturally occurring and less potentially toxic alternatives such as oils of cinnamon, thyme etc. Back in the early 80's Japanese researchers screened a variety of substances, including natural products and food additives, with known preservative properties but low toxicities and hoped to find synergistic combinations. Indeed Japanese patent specification JP A-57-194775 discloses an agent that is said to improve the preservation and quality of food containing cinnamic acid and another organic acid as effective components. The other organic acid can be citric, acetic, malic, fumaric, sorbic, tartaric or lactic acid. It is claimed that the combination of cinnamic acid and these other organic acids results in a synergistic antibacterial action. It is suggested that about 50 to 500 ppm cinnamic acid and from about 50 to 5000 ppm organic acid is used. These levels are used to preserve daikon (Japanese pickles), kamaboko (a boiled fish paste product), hampen (a Japanese cake made of pounded fish), Vienna sausage, mixed bean paste and flour paste. The specification does not mention any suitability for beverages, or tea.
EU legislation limits the use of sorbic acid to 300 ppm. There is no legal limit for cinnamic acid but the reported flavour usage within the industry is 31 ppm.
Cinnamon is a well known spice that is prized for its strong, distinctive and appealing flavour. Cinnamic acid is mainly used in the manufacture of methyl, ethyl, and benzyl esters for the perfume industry. The ethyl ester is used to make glass prisms and lenses. Other esters are used in medicine. The acid is also a known anthelmintic. The corresponding aldehyde is more pungent but is also used in the flavour and perfume industries.
The strong but not overbearing flavour of cinnamon together with its preservative ability and familiarity as a naturally occurring spice was recognised by the present inventors as being attractive as a key component of a flavouring system for use in ambient stable tea based beverages. Although there are some commercially available herbal teas that contain cinnamon, cinnamic acid is largely insoluble in low pH tea solutions.
The present inventors have now developed a preservative and flavouring system for tea based beverages which contains cinnamic acid in acceptably low concentrations in combination with an acidulant and optionally some additional preservatives which is particularly suitable for use in ambient-stable, tea based beverages.